Adult male rats had higher levels of norepinephrine and dopamine in several hypothalamic and forebrain nuclei. Castration of males on day 1 of life reduced adult levels of dopamine to female levels in the arcuate and diagonal band nuclei and administration of testosterone to females on day 4 of life raised dopamine levels in adulthood in these two regions. The neonatal androgen manipulations did not affect the sex differences in norepinephrine.